Highly active antiretroviral therapy has revolutionized the therapy of HIV disease, yet a substantial fraction of patients either never respond, or lose virologic control during the first 3 years of therapy. In this study, patients who have failed HAART were treated with three agents. The study had two major goals: (1) to determine the response rate to these agents, and (2) to determine what clinical and laboratory parameters, especially genotypic and phenotypic analysis, are useful for predicting response. Accrual of 98 patients has been completed; all have reached 48 weeks of followup. Results show that phenotypic assays are useful for predicting response to salvage regimens, and that toxicity is common, especially for patients with high viral loads. Genotypic assays were also useful for predicting response, but their interpretation is much more complex than for phenotypic assays. This manuscript will be published in AIDS in 2002.